Hi, I have a Sduro Hard seven SL Haibike with a 250w yamaha motor 2016 model. It has without any obvious reason stopped delivering assist but it still kicks in at times. I have checked contacts under the motor and changed batteries in controller, no error messages are displayed. It has a black ped Bluetooth device under the motor, not sure what this is . (bought s/h).Trying to find a fault or broken wire. So far no luck. Battery has not exceeded 200 charges.